The present invention relates to techniques for reducing noise in magnetic disk drives, and more particularly to a technique for reducing the noise occurring when the waving of the lubricating layer on the surface of a magnetic disk drive is processed.
In magnetic disk drives, magnetic heads for performing data read/write operations on the respective magnetic disks are each installed on an independent suspension assembly and positioned on a desired track by a voice coil motor (VCM). The operation that each magnetic head conducts to move from a track on the magnetic disk to another track is referred to as a seek operation. The magnetic head is formed on a slider having a shape of a rectangular parallelepiped. Hereinafter, the combination of the magnetic head and the slider is referred to as the head/slider. The head/slider has an air-bearing surface (ABS) formed on its face opposed to the magnetic disk. When a viscous air current that has occurred on the surface of the magnetic disk during its rotation flows through a wedge-shaped flow path formed between the ABS and the magnetic disk surface, the air current gives lifting force to the ABS and the head/slider flies upward to a position at which a balance is established between the lifting force and the pressure load applied from the suspension assembly. Hereinafter, the interval between the head/slider and the magnetic disk surface is referred to as flying height.
The head/slider is installed on the suspension assembly so that when the lifting force is given from the viscous air current, the head/slider can flexibly pivot to maintain a desired flying height, even against slight distortion of the magnetic disk. The head/slider is constructed so as usually not to come into contact with the magnetic disk surface. However, internal vibration, external physical shocks, or unstable behavior of the head/slider during the seek operation may cause contact with the magnetic disk surface. In recent years, flying height is further decreasing with the improvement of recording density, and the chance of the head/slider and the magnetic disk surface coming into contact with each other is also increasing.
A lubricating layer is formed on the surface of the magnetic disk since contact between the head/slider and the magnetic disk could lead to wear on or damage to both. In the situation where the head/slider follows a track for a fixed time at almost the same location, the air current flowing between the ABS and the magnetic disk surface pushes the lubricating layer away to its periphery, thus the lubricating layer moving in waves to make the flying height of the head/slider unstable. Patent Document 1 (Japanese Patent Laid-open No. 2003-151229) discloses a technique for activating the seek operation of a slider while monitoring the seek time thereof to prevent a lubricating film from waving. Patent Document 1 teaches that a seek operation not involving a read/write operation is made slower than the seek operation involving a read/write operation. The reasons for this, according to Patent Document 1, are that during a drive idle time, an actuator could collide with a crash stop at high speed in case of accidental electric power cutoff, and that a break-in process for the lubricating film needs to be made valid.